The present invention relates to a method in the reeling or winding of a web, in which method one or more factors or manipulated variables affecting the web in the reeling or winding are controlled during the reeling or winding by means of measurement data in order to affect the quality of the reel or roll formed in the reeling or winding.
In present-day reel-ups and intermediate reel-ups (rereelers) and slitter-winders, the reeling or winding is controlled indirectly by adjusting reeling parameters (linear load, web tension and circumferential/reeling force). The adjustment is typically conducted with a special program. The main objective of the reeling is to reel a roll from a continuous paper web, so that the roll meets the requirements set by the reeling process and further processing for processability and thereby for the structure of the roll as well as for the paper quality.
The properties of the web affect the quality of the roll. For example, the most common reeling problem caused by a poor web tension profile is the wrinkling of slack sections of the web, typically the edges, in the reeling nips, because the web is longer by the slack section than by the tense section. The slackness of the edges also produces a poor edge-zone structure in the roll, and results in edge rolls of poor quality, which are difficult to be wound by means of slitter-winders and which pose problems when used for example in printing machines. If the web tension profile is very fluctuating or e.g. one-sided, it can lead to the use of a high web tension to be quite sure, which loads the tense sections of the web more and increases the number of web breaks.
The structure of the roll is affected by manipulated variables of the reeling process, which typically include the linear load of the reeling nip, the circumferential force, and the web tension. The reeling of the paper web and its control by means of different variables are described for example in Finnish patent 89701 and in the corresponding European patent 483093. The control of the paper making process in a paper machine is also discussed more extensively in Finnish patent 94066, and in the corresponding U.S. Pat. No. 5,649,448. Here, a tension profile measurement provides information which is used to adjust the actuators which precede the measurement and affect the other transverse profiles of the web. Furthermore, publication JP-A-58162458 discloses a slitter-winder, in which the web is wound to form customer rolls. Here, the web tension is measured after unwinding, and it is displayed in a computer terminal, wherein the operator of the machine can set the values used in the unwinding to optimum.
The purpose of the invention is to present a reeling method, in which the properties of a web which is brought to reeling are better taken into account either in the reeling up of a full-width web or when winding a web to narrower customer rolls. To attain this purpose, the method according to the invention is primarily characterized in what will be presented in the characterizing part of the appended claim 1.
The invention comprises a control method for the reeling or winding process (e.g. reeling-up/intermediate reeling (rereeling), slitting/rewinding), in which method a web tension profile measurement is utilized to adjust the reeling or winding parameters and thereby the structure of the reel or roll to be reeled up or wound. The web tension profile is obtained in connection with the reeling up of a full-width web, i.e. web produced by a paper machine or a finishing machine for paper that has undergone a series of processing stages, in other words, it is possible to utilize the web tension profile information measured from the full-width web (the width of which, depending on the machine width, is several meters, typically over 4 meters). The variables to be adjusted in the reeling include for example the linear load of the reeling nip, the linear load profile, the center/circumferential drive and the web tension, or one or some of these. According to one embodiment, it is possible to profile a manipulated variable of the reeling or a factor affecting the web. For example the control of a spreading device, such as a spreader roll, preceding the reeling cylinder, also alleviates the problems of wrinkling in the reeling nip. By an active nip profile adjustment, it is also possible to control the effect of such local tension profile deviations on the structure of the web which are situated closer to the center of the web in the tranverse direction. It is also possible to adjust a suitable variable as a whole, for example the web tension level to reduce web breaks.
In slitter-winders, the need to adjust the structure of the roll due to a poor tension profile often pertains to edge rolls or individual rolls in the middle of the web. Center-drive slitter-winders enable a very accurate adjustment of the structures of individual rolls in each winding station. In the winding effected by the slitter-winder, it is possible to use, for example, the tension profile information from the reel-up of the full width web of the preceding process stage to adjust the reeling parameters.
The apparatus comprises at least a measuring device for the web tension profile, and a data processing unit which is arranged to process the information on the web tension profile and to control one or more controllers of the reeling or winding.